Conventionally, there has been proposed a noodle having a groove or slit formed along a longitudinal direction of the noodle with an objective of achieving a shortened cooking time. For example, Patent Literature 1 discloses a noodle having a single wedge-shaped groove with a depth of ½ to ⅘ of a diameter of the noodle having a substantially circular cross section. However, if the wedge-shaped groove reaches the center region in a cross section of the noodle, heat would easily penetrate not only the vicinity of the surface but also the center region in the noodle during cooking, so that, although cooking time of the noodle can be shortened as compared to a noodle without grooves, the noodle would be entirely softened and good texture could not be achieved.
In addition, Patent Literature 2 discloses a noodle formed with a solid center region having a circular cross section and a plurality of grooves each having a width that becomes wider at an innermost part than at an opening part. However, such grooves each having a width that becomes wider at an innermost part than at an opening part would not be sufficiently filled up but remain upon completion of cooking of the noodle, so that the noodle would have a different texture from that of a noodle without grooves and could not be improved in texture as a noodle without grooves.
Accordingly, it was difficult for the noodle disclosed in Patent Literature 1 or 2 to achieve “good texture (al dente) having a half-boiled core portion” that is pleasant to the taste as required of spaghetti, for example.
As a measure to cope with it, in an attempt to provide good texture (al dente) having a half-boiled core portion, Patent Literatures 3 and 4 each propose a grooved noodle formed with a plurality of grooves each of which has a cross sectional shape extending as spirally curving from a center region having a circular cross section to the surface of the noodle.